Pump



Dec. 5, 1961 D. N. GRIFFIN 3,011,451

PUMP

Filed May 7, 1953 2 Sheets-Sheet 2 INVENTOR .Dolmmo M zlrrm L a i BY ATTORNEY Patented Dec. 5, 1961 Mathieson Chemical Corporation, a corporation of Virginia Filed May 7, 1953, Ser. No. 353,461 1 Claim. (Cl. 103-166) My invention relates to a pumping device.

More particularly, my invention relates to a device which is suitable for use in the metering of a fixed volume of fluid, delivering the fluid from a first chamber or reservoir to a second chamber while the second chamber is at a relatively low pressure and then, after the delivery of the fluid to the second chamber, developing a positive seal of the inlet to the second chamber against superpressures (for example, greater than 10,000 p.s.i.g.) developed within the second chamber. A positive seal is maintained between the two chambers at all times.

I have in mind the application of my device to novel guns which employ liquid propellants such as monopropellant hydrazine. In such a case, a metered charge of the monopropellant is delivered to the gun chamber at a moderately low pressure, which need be sufficient only to feed the propellant within the time interval desired, after which the port or inlet through which the propellant is fed to the chamber is closed and sealed against the pressure developed by the burning of the propellant.

When used in such a gun, for example, my device provides certain important advantages. In the first place, positive scaling is maintained between the propellant reservoir and the gun chamber at all times, so that the danger of propagation of propellant burning, or dangerous pressures, back to the reservoir is eliminated. In the second place, my device is a positive displacement pump, and as a result accurate metering of a fixed quantity of propellant for each charge is maintained. In the third place, the pumping of the propellant is carried out at a low pressure, prior to the actual firing of the gun, so that power requirements for pumping are low, as compared to the case in which propellant is pumped into a gun at gun pressures, and also the problem of dynamic sealing (involving the use of moving seals) against gun pressures is eliminated. In the fourth place, the gun chamber is closed and sealed by means of static (stationary) seals during the period of actual firing when superpressures are developed. Finally, my pump lends itself to gun operation, either single-fire or automaticfire, and is adaptable to small caliber weapons, such as an infantry type rifle, as well as to larger caliber automatic guns, such as a 20 to 37 mm. machine gun.

For a more complete understanding of my invention, reference is made to the accompanying drawings in which FIGS. 1 to 412 show in cross-section an embodiment of my invention in various phases of its operating cycle and FIG. shows in cross-section the manner in which my device can be actuated by the gas pressure developed within a gun barrel when the gun is fired. In order to show my device in sufiicient detail the cross-sectional views have been cut in half so that FIGURES 1a, 2a, 3a and 4a represent longitudinal extensions of the upper portions of FIGURES l, 2, 3 and 4 respectively.

Referring specifically to FIGS. 1 to 4a, my device comprises a cylinder 1 fitted with a piston 2 which is integrally attached to shaft 3. Sleeve 4 is slidably, mounted on shaft 3 but at certain times during the operating cycle of the device is held in such manner that axial movement with respect to shaft 3 does not occur. This is effected by means of suitable detent or locking means such as spring-loaded ball latches which engage detent grooves 5 and 6. Spring 7 is provided to move or push shaft 3 and spring 8 also moves or pushes shaft 3 at particular periods in the operation of the device to be described later. Spring 7 is stronger than spring 8, and by this I mean that the compression force exerted on spring 7 is at all times greater than the force required to compress spring 8 completely. This does not mean, however, that spring 8 is never free to expand during the operating cycle of the device.

The operation of my device is as follows:

FIGS. 1 and 1a show the piston 2 in its rearmost position with a measured charge of propellant 9 contained in the annular space between the cylinder 1 and the shaft 3. Sleeve 4 is locked to shaft 3 by means of the springloaded ball latches which are in engagement with detent groove 5. Spring 7 drives the shaft 3, piston 2 and sleeve 4 forward until sleeve 4 contacts movable stopping means such as sleeve 10, as shown in FIGS. 2 and 2a.

Sleeve 4 then remains stationary while shaft 3 and piston 2 continue moving forward under the action of spring 7 to the position shown in FIGS. 3 and 3a, releasing the ball latches from detent groove 5 and forcing the liquid charge of propellant 9 through port 11 into the second chamber (not shown) in which the superpressure is later developed, for example, a gun chamber. At the time piston 2 contacts sleeve 4 the ball latches engage detent groove 6 to again latch sleeve 4 to rod 3. When piston 2 contacts sleeve 4, spring 7 is no longer free to expand, inasmuch as at one end it is in abutment with a collar on shaft 3, as shown in FIGS. 1 to 4a, and at the other end it is in abutment with sleeve 10, which is in abutment with sleeve 4. Sleeve 4 in turn is in abutment with piston 2, which, as has been stated, is integral with shaft 3. Spring 3 then becomes free to expand and it then moves shaft 3, piston 2, spring 7 and sleeves 4 and 10 forward to the position shown in FIGS. 4 and 4a, at which point sleeve 4 contacts fixed stopping means 12 and the second chamber, for example, a gun chamber, is closed by the piston 2.

After the superpressure has been developed in the second chamber, the return stroke of the piston can be accomplished in various ways, for example, manually, by pressure developed within the second chamber, or by recoil energy. The return stroke compresses springs 7 and 8, and also recharges the liquid propellant 9 as follows:

Sleeve 4 is locked to shaft 3 as shown in FIGS. 3, 3a, 4 and 4a by the ball latches engaging detent groove 6. As the shaft 3 moves back, sleeve 4 and piston 2. are in contact with each other and move rearward in closed position until sleeve 4 is stopped by releasable stopping means such as spring-loaded latch 13. The piston 2 continues rearward, releasing the ball latches from detent groove 6 and charging propellant 9 from the reservoir or first chamber (not shown) through port 14. When piston 2. reaches its rearward position, the ball latches engage detent groove 5 and the pump is then ready to begin another cycle of ope-ration.

The pressure in the reservoir need be maintained only sufliciently high to give a satisfactory flow rate into the annulus between the cylinder 1 and shaft 3 as that annulus is created by piston 2 as it moves to its rearmost position.

Any suitable seals against fluid leakage may be used on piston 2, shaft 3 and sleeve 4. In the specific embodiment shown in the drawings, O-rings 15 are shown. This type of seal is satisfactory as a dynamic seal for the low pressures encountered during pumping and as a static seal against superpressures when they are developed in the second chamber.

FIG. 5 represents in highly diagrammatic form one way in which the superpressure developed within the second chamber can be used to actuate the pump which I have invented. In FIG. 5 the numeral 3 represents the shaft heretofore described and as shown it is provided at the end with piston 16 positioned within cylinder 17 which communicates by means of port 18 of gun barrel 19. Pressure developed within the gun when the gun is fired exerts a force on piston 16 and thereby can move my device into the position shown in FIG. 1a.

I claim:

A reciprocating pump suitable for use in delivering a quantity of fluid from a reservoir into a chamber at relatively low pressure and thereafter sealing said chamber when superpressures are later developed therein, the said pump comprising a cylinder provided with an inlet port communicating with said reservoir and an outlet port communicating with said chamber, a piston positioned Within said cylinder and integrally attached to a shaft longitudinally positioned within said cylinder, a sleeve slidably mounted upon said shaft, releasable stopping means preventing the movement of said sleeve along said shaft beyond a fixed position in the direction of said piston so that when the piston is at the rearward end of its 44 stroke an annular space is defined by said piston, shaft, cylinder and sleeve in communication with said inlet port whereby a volume of fluid can enter said annular space from said reservoir and also so that said sleeve closes said outlet port, a stronger spring urging said shaft, piston and sleeve in the direction of the forward end of their stroke, first releasable locking means adapted to maintain said shaft and sleeve in constant relative position until in its forward motion said sleeve contacts movable stopping means thereby causing said first releasable locking means to release and no longer maintain said shaft and said sleeve in constant relative position, said movable stopping means being so positioned that when it causes said first releasable locking means to release said outlet port is at least partially uncovered by said sleeve and the rearward end of said sleeve is not further forward than the forward end of said exit port, second releasable locking means adapted to maintain said shaft and sleeve in constant relative position when said piston in its further forward motion in ejecting the volume of fluid through said outlet port contacts said sleeve and adapted to release when said releasable stopping means prevents the movement of said sleeve along said shaft, and a weaker spring urging said movable stopping means, stronger spring, piston, shaft and sleeve forward until said sleeve contacts fixed stopping means and said outlet port is covered by said piston.

References Cited in the file of this patent FOREIGN PATENTS 9,791 Great Britain of 1889 197,518 Great Britain May 17, 1923 1,003,687 France Nov. 21. 1951 

